KR20060125798A - Method and apparatus for generating a look-up table in the video picture field - Google Patents

Abstract

The present invention is particularly useful in the field of plasma display panels (PDPs) or other display devices wherein each video level is represented by a combination of bits according to a specific coding. In this case, when the algorithms used to improve picture quality are based on data stored in memories such as look- up tables (LUTs), the size of such tables may be quite huge. To improve picture quality in PDPs, an algorithm using metacode LUTs has been developed, using data stored in look-up tables. The invention proposes a way to reduce the amount of look-up tables needed for implementing metacodes. According to the invention, only some look-up tables of low size are stored and the other ones are achieved by extrapolation.

Description

METHOD AND APPARATUS FOR GENERATING A LOOK-UP TABLE IN THE VIDEO PICTURE FIELD}

The present invention relates to a method for generating a look-up table in a video picture field. The invention also relates to a circuit for implementing the method.

The invention is particularly useful in plasma display panels (PDPs) or other display device fields where each video level is represented by a combination of bits according to a particular coding. In this case, when the algorithm used to improve the picture quality is based on data stored in a memory such as a lookup table (LUT), the size of such a table can be quite large.

To understand this problem, the present invention is described in the context of PDPs, but is applicable to other types of displays or other devices that process video data and require memory with large sizes.

In order to improve picture quality in PDPs, many algorithms have been developed using data stored in lookup tables. For example, EP patent application 1 353 314 describes a method for improving gray scale fidelity portrayal based on a modification of the coding approach for each average power level (APL) that occurs in every frame. This is based on the metacode concept in which subfield codes based on subfield weights are replaced with metacodes based on subfield actual luminance. More specifically, for a given peak white level, sustain pulses are distributed to a subfield, and the number of pulses in the subfield corresponds to its weight. Subfield codes are then mapped to luminance codes, which are reordered in a certain order. In addition, the video levels are mapped to the available brightness codes and processed to achieve intermediate levels of brightness. The luminance code is then mapped to the output subfield code. In this case, a lookup table is used to map at least the video level to the luminance code and to map the luminance code to the output subfield code. For example, these lookup tables containing luminance codes to be loaded for each new APL value are stored in external memory. These tables, called metacode lookup tables, are quite large.

1 is a standard implementation circuit of a metacode coding unit as described in EP patent application 1353314. This unit includes a first memory 100 comprising 1024 x 12 bits to handle 10 bits of the input video resolution. A first metacode lookup table is stored in this memory and used to map video levels to available luminance codes. This first metacode lookup table may or may not include a degamma function. Each time the APL value changes, a new metacode lookup table is loaded into memory 100. At the output of the memory 100, a 12-bit video signal is obtained. Available 12 bits correspond to integer resolution of 8 bits and fractional resolution of 4 bits. Thereafter, a 12-bit video signal YA [11-0] is sent to the dithering circuit 110. In this circuit 110, a 4-bit fractional resolution is added using 4-bit dithering and then truncated.

YB [7, 0], the video signal from circuit 110, is then sent to second memory 120, which includes 256 x 16 bits. A second lookup table is stored in the memory 120 and used to implement the transcoding step, which is the step of mapping the luminance code to the output subfield code.

As described above, the memory 100 needs to be updated using a new metacode lookup table whenever the APL value changes. Lookup tables are provided for each APL value. These lookup tables are stored in external memory 130, such as flash memory, EEPROM, and the metacode lookup table, for each video level and a given APL value, is a 12-bit code representing the luminance code to be generated to achieve the video level. To qualify. For a 10-bit APL value, you need an external memory with a size of 1024 × 1024 × 12 = 12 megabits.

Also, if different metacode lookup tables are needed for each color, the overall size of memory 130 is increased to 36 megabits. In addition, for each display mode used in the plasma display panel, since the metacode lookup table is different, such as 60 ms, 50 ms and 75 ms, the need for external memory is further increased to 108 megabits for the three modes.

Therefore, one major problem with the implementation circuit of FIG. 1 is the large size of the external memory 130.

It is an object of the present invention to propose a method of reducing the amount of data needed to implement the metacode method by using a low number of metacode lookup tables and extrapolating the others.

In a general manner, the invention relates to a method of generating a lookup table with respect to a parameter of a given value among N different values, wherein the output value is a piecewise linear of the variable {S (VAL)} that depends on the given value. Can be approximated by a function.

The method of the present invention can be used to generate a metacode lookup table for a given value of average power level.

The method of the present invention can also be used to generate another lookup table in a video picture field.

Thus, the present invention provides a method of generating a lookup table for a given value of a parameter among N different values, the output value of which can be approximated by a delimited linear function of the variable according to the given value,

Dividing the set of N values into P subsets of consecutive values, each piece of the distinct linear function being in a different subset,

Defining a lookup table for two boundary values of each subset (i), called a primary lookup table and a secondary lookup table, respectively;

For each subset i, defining a delta lookup table corresponding to the difference between the secondary lookup table and the primary lookup table associated with the subset i;

For each of the N values, the extrapolation coefficient according to the value of the variable S for a given value and the value of the variable S for two boundary values of the subset i containing the given value Defining steps and

Calculating a lookup table for a given value, according to the associated extrapolation coefficients, the primary lookup table and the delta lookup table.

It is characterized by including.

In the embodiment described herein, the generated lookup table is a metacode lookup table, the parameter is the average power level, and the variable is the number of sustain pulses corresponding to the given value of the parameter.

The boundary level associated with the primary lookup table of the subset of average power level values is the highest average power level value of the subset, and the boundary level associated with the secondary lookup table of the subset of average power level values is the most significant of the subset. Low average power level value.

와 같이 한정되며, 여기서 S_MAX는 최고(peak) 흰색 이미지에 관한 변수의 값(S)이고, S_MIN은 완전한 흰색 이미지에 관한 변수의 값이다. 외삽 계수는

와 같고, 여기서 S(PMTC_i)는 서브세트(i)의 가장 높은 경계값에 관한 변수의 값(S)이며, S(SMTC_i)는 서브세트(i)의 가장 낮은 경계값에 관한 변수의 값(S)이고, S(VAL)는 주어진 값에 관한 변수의 값이다.Preferably, the ratio between the value of the variable for one boundary value in subset i and the value S of the variable for the same boundary value in subset i + 1 is a fixed parameter α. ), And this parameter (α)

Where S _MAX is the value of the variable (S) for the peak white image and S _MIN is the value of the variable for the full white image. Extrapolation factor

Where S (PMTC _i ) is the value S of the variable with respect to the highest boundary of subset (i) and S (SMTC _i ) is the value of the variable with respect to the lowest boundary of subset (i). Is the value S, and S (VAL) is the value of the variable with respect to the given value.

The calculated lookup table is based on the output of the primary lookup table PMTC _{i for} a given value VAL and the delta lookup table for a given value VAL weighted by the extrapolation coefficient for the given value VAL. PMTC _i ) is equal to the sum of the outputs.

The present invention is also a device for generating a lookup table for a given value of a parameter among N different values, the output value of which can be approximated by a distinct linear function of the variable according to the given value, the set of N values Is a lookup table generation device, wherein P is divided into P subsets of consecutive values, each of the distinct linear functions being in a different subset,

A first memory, for each subset i, storing a primary lookup table associated with one boundary value of said subset i;

For each subset i, a second memory for storing a delta lookup table corresponding to the difference between the secondary lookup table and the primary lookup table associated with the subset i, the secondary lookup table being a sub A second memory, associated with another boundary value in the set (i),

A third memory for each of said N values, storing an index indicating which primary lookup table in the first memory and which delta lookup table in the second memory should be used for extrapolation,

A fourth memory for storing an extrapolation coefficient for each of said N values, wherein said extrapolation coefficient associated with one given value comprises a value of a variable S for said given value and said given value A fourth memory defined by the value of the variable S relating to the two boundary values of the subset i to

A calculation block that generates a lookup table for a given value according to the associated extrapolation coefficients, the primary lookup table and the delta lookup table.

It is characterized by including.

The above described method can be implemented in this device.

Exemplary embodiments of the invention are shown in the drawings and described in more detail in the following description.

1 schematically illustrates one embodiment of a method of the prior art;

2 schematically illustrates one possible implementation of the method according to the invention.

The present invention is described with reference to generating metacode lookup tables for different average power levels, i.e., APL values.

It is an object of the present invention to reduce the number of lookup tables required. Only some lookup tables are predefined for some APL values, and for other APL values a new lookup table will be extrapolated from these predetermined lookup tables.

In the following description, the metacode LUT specified for a given APL value defines the output level representing the luminance code to be used for each input video level.

In accordance with the present invention, and as illustrated by FIG. 2, four lookup tables with a smaller overall size than the size of the memory 130 of FIG. 1, and the following metacode lookup table for all APL values with an evaluation block: Used to implement In other words,

A first lookup table (LUT1) comprising 16 metacode LUTs of its own, called a primary metacode LUT, each primary metacode LUT containing metacodes associated with a particular APL value, called a primary APL value; The primary APL value is described below in this specification.

A second lookup table (LUT2) comprising 16 delta LUTs corresponding to the difference between the secondary metacode LUT and the primary metacode LUT, wherein each secondary metacode LUT is a particular APL called secondary APL value; Metacodes associated with the values are included, and the secondary APL values are described below in this specification.

For each APL value, a third lookup table (LUT3) containing an index indicating which primary metacode LUT in LUT1 and which delta LUT in LUT2 should be used for extrapolation,

For each APL value, a fourth lookup table (LUT4) containing the coefficients to be used for extrapolation and

Extrapolation block (EXTRAPOL) to calculate LUT

As mentioned above, each subset of APL values includes a primary APL value and a secondary APL value. This set of APL values includes, for example, 1024 values from 0 to 1023, and is divided into, for example, 16 subsets of consecutive APL values. The primary APL value is the highest APL value of the subset (corresponding to the smallest number of sustained pulses), and the secondary APL value is the lowest APL value of the subset (corresponding to the highest number of sustained pulses). The primary metacode LUT is defined for each primary APL value. These primary metacode LUTs are stored in LUT1. Secondary metacode LUTs are defined for each secondary APL value, but these secondary metacode LUTs are not stored in LUT1 or LUT2. These are only used to calculate the delta LUT stored in LUT2.

For each APL value, the lookup table (LUT3) carries a pointer on the primary metacode LUT that should be used to generate the metacode LUT of this APL value. LUT3 has 10 bits of input and 4 bits of output to select one of the 16 primary metacode LUTs.

The notation used herein is as follows.

PMTC _i represents the primary metacode LUT related to the subset _i of APL values.

S (PMTC _i ) represents the number of sustain pulses with respect to the APL value (primary APL value) corresponding to the primary metacode LUT (PMTC _i ).

PMTC _i (V) represents the output of the primary metacode LUT PMTC _i with respect to video level (V).

SMTC _i represents the secondary metacode LUT related to a subset (i) of APL values.

S (SMTC _i ) represents the number of sustain pulses with respect to the APL value corresponding to the secondary metacode LUT SMTC _i .

SMTC _i (V) represents the output of the secondary metacode LUT SMTC _i for video level (V).

S (X) represents the number of sustain pulses relative to the APL value (X).

Some jumps may appear when there is a switch from one primary metacode LUT to another primary metacode LUT. For example, the smallest subfield code value (e.g. one sustain pulse) has a different (different compared to any value?) Relative value (such as the total number of 1 / sustain pulses), which means that the total number of sustain pulses This is because it changes from one primary metacode level to another primary metacode level (from one APL value to another APL value). These two different values of ratio (such as the ratio of two different total numbers of sustain pulses of two primary metacode LUTs) can make a jump.

In order to have nearly the same visibility of the possible jumps when switching from one primary metacode to another, these ratios must be as follows.

This means that partitioning takes place in an algebraic way. The previous formula means that the second, third and fifteenth subsets of APL values have the same ratio between their smallest APL value and their highest number of sustain pulses. If this ratio α is also imposed on the first subset,

Where S _MAX is the number of sustained pulses for the highest white (low APL value).

If you multiply all terms together,

Where S _MIN is the number of sustained pulses for a complete white image.

이고, S(PMTC_i) = S_MIN ×α^15-i이다.therefore,

And S (PMTC _i ) = S _MIN X alpha ^15-i .

This algebraic split is the only suggestion to have the same visibility of possible jumps when switching from one primary metacode LUT to another, but it is possible to use different splits of the APL set. For example, it is possible to use different partitions to have more subsets for low values of APL and less subsets for high values of APL.

In the example given in the appendix below, the set of APL values is divided into 16 subsets. Primary APL values (lowest APL values in each subset) are shown in bold text, and secondary APL values (highest APL values in each subset) are shown in black areas.

This example is given for the following inputs.

Super white image: 1100 continuous pulses

Fully white image: 200 continuous pulses.

Parameter α is

과 같다.

Same as

The 16 primary APL values used for the primary metacode LUT are determined as indicated in the appendix table. The maximum number of sustain pulses of the first order metacode LUT PMTC _i is 200 × α ⁱ sustain pulses, where i = 0..15.

The APL value is distributed as follows.

APL value from 0 to 135 ⇒ Subset 15

APL value from 136 to 230 ⇒ Subset 14

APL value from 231 to 318 ⇒ Subset 13

APL value from 319 to 398 ⇒ Subset 12

APL value from 399 to 473 ⇒ Subset 11

APL value from 474 to 540 ⇒ Subset 10

APL value from 514 to 604 ⇒ Subset 9

APL value from 605 to 663 ⇒ Subset 8

APL value from 664 to 716 ⇒ Subset 7

APL value from 717 to 766 ⇒ Subset 6

APL value from 767 to 812 ⇒ Subset 5

APL value from 813 to 856 ⇒ Subset 4

APL value from 857 to 898 ⇒ Subset 3

APL value from 899 to 938 ⇒ Subset 2

APL value from 939 to 978 ⇒ Subset 1

APL value from 979 to 1023 ⇒ Subset 0

As an example, for subset 15, the primary APL value is 135 and the secondary APL value is zero. The maximum number of sustain pulses for the primary metacode LUT is 988 and the maximum number of sustain pulses for the secondary metacode LUT is 1100. The metacode LUT related to the APL value contained between 1 and 134 of subset 15 is computed by extrapolation. It is extrapolation in that it is not interpolation between two metacode LUTs related to different subsets. These metacode LUTs associated with the APL values (1 ... 134) may be achieved by interpolation between the primary metacode LUTs associated with the APL values 135 and the secondary metacode LUTs associated with the APL values (0). . Secondary metacode LUTs are used only for extrapolation.

In a preferred embodiment, the extrapolation of the APL values of the subset (i) is the primary meta-code LUT PMTC _i and a first meta-code LUT PMTC _i and the second meta-code LUT delta LUT corresponding to the difference between the SMTC _i Is done between. This differential LUT, denoted LUT2 _i , is stored in the lookup table LUT2. The value in the delta LUT included in this LUT2 may be positive or negative, but 8-bit resolution is sufficient.

The value stored in the delta LUT related to the subset (i) in LUT2 and precomputed with respect to the video level (V)

(Why coefficient 64/63?)

Preferably, more resolution should be used for PMTC _i (V) and SMTC _i (V) than is available for LUT1 to evaluate the lookup table LUT2.

The extrapolation coefficients for APL values used for extrapolation and belonging to subset (i) labeled C (APL) are the difference between NbSustain (APL) and S (PMTC _i ), the number of sustain pulses in the current APL, and S (SMTC _i). ) And S (PMTC _i ). As for this coefficient, 6 bit resolution is sufficient.

(Why coefficient 63?)

The final extrapolation

Output (V) = LUT1 _i (V) + (LUT2 _i (V) × C (APL)) / 64

(Why coefficient 64?)

The primary metacode LUT is independent of the principles of the present invention. Only other metacode LUTs are achieved from these primary metacode LUTs.

One possible embodiment of the method of the invention is illustrated by FIG. 2 as indicated below. The lookup tables LUT1, LUT2, LUT3, LUT4 are stored in four memories 101, 102, 103, 104. These may be included in an external memory (EPROM or FLASH) which can be read bit by bit by the controller. Extrapolation is calculated by extrapolation block 105. This block is connected to the dither block 110 in FIG. In normal operation, at the end of every frame, the new LUT1 _i and LUT2 _i The data must be downloaded by the controller according to the APL value calculated during the portion in which the video signal based on the video data is active.

This method requires only (16 × 1024 × (12 + 8) + 1024 × (6 + 4)) × 3 × 3 = 2.9 megabits for three modes instead of 108 megabits using the method implemented in FIG. Shall be.

As noted above, the present invention is applicable to a plasma display panel (PDP) or other display device field where each video level is represented by a combination of bits according to a particular coding.

Claims (14)

A method of generating a lookup table for a given value VAL of a parameter APL among N different values, the output value of which is to be approximated by a distinct linear function of the variable S (VAL) according to the given value. In the look-up table generation method, Dividing the set of N values into P subsets of consecutive values, each piece of the distinct linear function being in a different subset, Defining a lookup table for the two boundary values of each subset _i called primary lookup table PMTC _i and secondary lookup table SMTC _i , respectively; For each subset i, defining a delta lookup table corresponding to the difference between the secondary lookup table SMTC _i and the primary lookup table PMTC _i associated with the subset _i ; For each of said N values, a variable S (VAL) of a variable S with respect to a given value VAL, and a variable with respect to two boundary values of a subset i containing the given value, Defining an extrapolation coefficient C (VAL) according to the values S (PMTC _i ) and S (SMTC _i ) of S; and Calculating a lookup table for a given value VAL, according to the associated extrapolation coefficient C (VAL), the primary lookup table PMTC _i and the delta lookup table. And a lookup table generation method. The method of claim 1, wherein the lookup table is a metacode lookup table, the parameter is an average power level, and the variable S (VAL) is the number of sustain pulses corresponding to a given value VAL of the parameter. A lookup table generation method. 3. The boundary level associated with the primary lookup table PMTC _i of the subset of average power level values is the highest average power level value of the subset and the secondary lookup of the subset of average power level values. And the boundary level associated with the table (SMTC _i ) is the lowest average power level value of the subset. 4. The same boundary value according to any one of claims 1 to 3, wherein the value S (PMTC _i ) of the variable with respect to one boundary value in the subset (i) and the same boundary value in the subset (i + 1). And the ratio between the value of the variable S (PMTC _{i +1} ) in relation to is equal to the fixed parameter α. The method according to claim 4, wherein the parameter α is

Wherein S _MAX is the value of the variable S with respect to the peak white image and S _MIN is the value of the variable with respect to the complete white image. The method according to any one of claims 1 to 5, wherein the extrapolation coefficient C (VAL) is

Same as Where S (PMTC _i ) is the value of the variable with respect to the highest boundary of subset (i), S (SMTC _i ) is the value of the variable with respect to the lowest bound of the subset (i), S (VAL) is a value of a variable with respect to a given value. 7. The calculated lookup table is weighted by the output of the primary lookup table PMTC _{i for a} given value VAL and the extrapolation coefficient for a given value VAL. Is equal to the sum of the outputs of the delta lookup table PMTC _{i for} a given value VAL. A device for generating a lookup table for a given value VAL of a parameter APL among N different values, the output value of which is to be approximated by a distinct linear function of the variable S (VAL) according to the given value. Wherein the set of N values is divided into P subsets of consecutive values, each of the discrete linear functions being a lookup table generation device in a different subset, A first memory 101 storing, for each subset i, a primary lookup table PMTC _i associated with one boundary value of the subset _i ; For each subset _i , a second memory for storing a delta lookup table corresponding to the difference between the secondary lookup table SMTC _i and the primary lookup table PMTC _i associated with the subset _i ; 102, wherein the secondary lookup table SMTC _i is associated with another boundary value of the subset i; A third storing an index indicating, for the N values, which primary lookup table in the first memory 101 and which delta lookup table in the second memory 102 should be used for extrapolation; Memory 103, A fourth memory 104 for storing an extrapolation coefficient C for each of said N values, said extrapolation coefficient C (VAL) associated with said one given value being said given value VAL. Value S (VAL) of variable S with respect to) and values S (PMTC _i ), S (with respect to the two boundary values of the subset i containing the value given above. Fourth memory 104, defined in accordance with SMTC _i )) and Calculate block 105 for generating a lookup table for a given value VAL according to the associated extrapolation coefficient C (VAL), the primary lookup table PMTC _i and the delta lookup table. And a lookup table generation device, characterized in that it comprises a. 9. The metacode lookup table of claim 8, wherein the parameter is an average power level, and the variable S (VAL) is a number of sustain pulses corresponding to a given value VAL of the parameter, and a metacode lookup table for each average power level value. Generating a lookup table. 10. The method of claim 9, wherein the threshold associated with the primary lookup table PMTC _i of the subset of average power level values is the highest average power level value of the subset, and the secondary lookup of the subset of average power level values. A lookup table generating device, characterized in that the boundary value associated with the table SMTC _i is the lowest average power level value of the subset. The same boundary value according to any one of claims 8 to 10, wherein the value S (PMTC _i ) of the variable with respect to one boundary value in the subset (i) and the same value in the subset (i + 1). A look-up table generation device, characterized in that the ratio between the value of the variable S (PMTC _{i +1} ) in relation to is equal to a fixed parameter α. 12. The method according to claim 11, wherein said parameter [alpha] is

Wherein S _MAX is the value of the variable S for the highest white image and S _MIN is the value of the variable S for the complete white image. 13. The method according to any one of claims 8 to 12, wherein the extrapolation coefficient C (VAL) is

Same as Where S (PMTC _i ) is the value of the variable with respect to the highest boundary of subset (i), S (SMTC _i ) is the value of the variable with respect to the lowest bound of the subset (i), S (VAL) is a value of a variable with respect to a given value. The calculated lookup table is weighted by the output of the primary lookup table PMTC _{i for a} given value VAL and the extrapolation coefficient for the given value VAL. Device, characterized in that the sum of the outputs of the delta lookup table PMTC _{i for} a given value VAL is given.

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